An electronic key system verifies an electronic key by performing wireless communication with an electronic key. When the electronic key is verified, the locking and unlocking of vehicle doors and the starting of the engine is performed. In such an electronic key system, encrypted communication is performed between the electronic key and the vehicle to maintain a certain level of security. This allows for the electronic key to be verified with a high level of confidentiality.
The common key cryptosystem is one type of an encryption standard. In an electronic key system that uses the common key cryptosystem, when registering an electronic key to a controller of a vehicle, the electronic key and the vehicle both store the same encryption key. The controller uses the encryption key to communicate with and verify the electronic key by comparing identification information that is transmitted from the electronic key with identification information that is stored in the controller.
Japanese Laid-Open Patent Publication No. 2011-20475 describes an electronic key registration system that registers an electronic key to a controller by storing an encryption key in the controller and the electronic key. In the electronic key registration system, a data center communicates with the electronic key and the controller to store an encryption key in the electronic key and the controller and associate the electronic key with the controller. This prevents an unauthorized electronic key from being registered to the controller.
When registering a plurality of electronic keys in the electronic key registration system of the prior art, the electronic keys are required to be registered one by one. Thus, whenever an electronic key is registered, communication is performed between the data center and the electronic key and between the data center and the controller. That is, communication with the data center is repeated for a number of times that is the same as the number of electronic keys that are to be registered. Accordingly, the registration of electronic keys is burdensome. This problem occurs not only when the electronic key system is applied to a vehicle but also when applied to a building such as a house.